An optical-type sensor is known from EP 133506081, which allows to detect in use the turbidity of a washing fluid in an electric household appliance by means of optical absorbance measures. Such measures are used by the electric household appliance to check the correct performance of the set washing cycle and/or to adapt the washing cycle to the dirt conditions of dishes or laundry being washed.
The known sensor has a fork-shaped casing with two “fingers”, a first one accommodating a photo emitting element at the tip, and the second one accommodating a photo receiving element; furthermore, a temperature sensor is also provided on the longest “finger”. The two photo emitting and photo receiving elements thus allow to measure the absorbance of a fluid between the two “fingers”, in order to evaluate the turbidity of the fluid itself.
The known sensor has several drawbacks. Firstly, it is rather large in size, especially in the transversal direction. Secondly, it does not allow any sensor reading calibration except at the electronic level, e.g. using a microprocessor, which is a costly and complex solution. Thirdly, the distance between emitter and receiver may be influenced by possible deformations of the “fingers” which may occur in use, thus compromising the sensor accuracy. It is also complex to be assembled on the electric household appliance due to the prismatic shape of the casing.